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Sending Data over Offline Finding Networks

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103 pointsfindmysanity9 comments

Bluetooth and specifically BLE is way more capable and versatile than most people understand. We are using it for a connectionless time synchronisation protocol that also contains a rudimentary control plane.

The clients can receive synchronisation data every minute and listen for a year on a coin cell. It’s broadcast, so a single beacon node can service hundreds of clients simultaneously.

BLE also can manage data connections over a kilometer and a half with reasonable (not great) antennas.

It’s not terribly fast, but modern radio protocols are opening up the possibilities. Lora and BLE are bringing the environment alive with communication.

Hubble Network (https://hubble.com) is building something similar - an open, global BLE network.

Both let you transmit arbitrary data, but the custom setup here is a lot of overhead. Hubble gives you an SDK and lets you get back to building your device.

> Apple’s Unwanted Tracking (UT) alerts show a notification when a suspicious device is detected moving with the user for at least 840 meters and 10 mins. [...] This suspicious lost device must be an AirTag or AirPod that is separated from its owner and broadcasting rolling public keys.

So if I turn my phone off and get onto a bus or train with a tracking tag, other passengers will get an alert?

Also, the wording indicates that the tag needs to be marked as lost. But could that be used as plausible deniability -- that someone had stolen it -- by a person engaged in illicit tracking?

If you get on the bus with it, wouldn’t it not count as “separated from its owner”? Your phone, after all, sends out these pings as well even when off. So, the tag may know it’s with the phone even then. Also I don’t think it has to be “marked as” lost. This stuff doesn’t depend on anything that the owner of the tag gets to configure, since the point is to make it harder to abuse this way. I do think it’s dumb though. A real GPS tracker is not expensive - this stuff is only deterring the least-dedicated stalkers.

It probably wouldn't trigger, because of the 2nd criteria:

> The alert is not triggered immediately: it takes 8 hours during the day, 30 mins at night, and ...

But the warning system is by no means perfect. My family is split 50-50 between iOS and Androd ecosystems, and that's already enough to throw things off and get false positives semi-regularly.

Also, don't even ask the curriers how many alerts they get. Including airtags in valuable shipments is the de-facto standard nowdays.

No. Those alerts depend on the device type, so it must be an airtag or airpod. The following line makes that more clear.

> In the BLE advertisement, any beacon marked as either an Apple Device or Find My Device using the status byte will not generate stalking alerts.

I think it is kind of scary that they bypassed the stalking protections just by changing the device ID constantly. It is really clever engineering to use random peoples phones as a data mule but it feels like a security hole.

Ah I always wondered if you could avoid the unwanted tracking warning by cycling through virtual devices. Slightly disappointing that you don't even need to resort to that.

Interesting research. Could have done with some motivation - why would you want to do this exactly? And it's a shame they couldn't get it to work with Google's network (in a non-awful way anyway).

This is brilliant and can be quite useful, in fact maybe as a backup to a traditional IoT network such as LoRA, as an immediate use-case - piggy-backing Apples network to extend IoT seems like a reachable fruit ..

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